The present invention relates to a cutting insert in which at least one cutting-edge element, made of a sintered section containing a super-hard substance such as diamond, or the like, is mounted on a corner of a base plate.
Conventionally, the cutting insert of the kind referred to above has formed therein a chip breaker of a superior finely finished surface in order to enable the discharge of chips in a superior manner.
However, the conventional cutting insert has a drawback or disadvantage in that it is difficult for the chips to be curled into spiral form by the chip breaker.
In order to solve the above-discussed problem, various experiments have been performed. As a result, the following knowledge has been obtained. That is, in the case where a super-hard sintered section is used, the cutting quality or sharpness is improved, and the cutting resistance is reduced. In addition thereto, since the cutting insert is formed such that the surface roughness of the chip breaker is extremely low, the chips flow extremely smoothly on and along the chip breaker. Thus, the chips are discharged without being curled on the chip breaker; that is, it is difficult for the chips to be curled.
Apart from the above, cutting inserts are conventionally known in which a plurality of chip breakers of identical form are provided respectively at the corners of a base plate.
In the cutting insert constructed as above, the cutting insert is replaced by other types depending on the kind of cutting, such as rough cutting, finishing, and the like, to be performed.
However, the conventional cutting insert described above has the following problem: since the chip breakers are identical in form to each other, the cutting inserts must be replaced with other ones, when rough cutting is completed and subsequent finishing is to be continuously performed.
Thus, the following problem arises. That is, the cutting operation is troublesome and cumbersome, and operational efficiency is reduced.